ima: Fix NULL pointer dereference in ima_file_hash
ima_file_hash can be called when there is no iint->ima_hash available
even though the inode exists in the integrity cache. It is fairly
common for a file to not have a hash. (e.g. an mknodat, prior to the
file being closed).
Another example where this can happen (suggested by Jann Horn):
Process A does:
while(1) {
unlink("/tmp/imafoo");
fd = open("/tmp/imafoo", O_RDWR|O_CREAT|O_TRUNC, 0700);
if (fd == -1) {
perror("open");
continue;
}
write(fd, "A", 1);
close(fd);
}
and Process B does:
while (1) {
int fd = open("/tmp/imafoo", O_RDONLY);
if (fd == -1)
continue;
char *mapping = mmap(NULL, 0x1000, PROT_READ|PROT_EXEC,
MAP_PRIVATE, fd, 0);
if (mapping != MAP_FAILED)
munmap(mapping, 0x1000);
close(fd);
}
Due to the race to get the iint->mutex between ima_file_hash and
process_measurement iint->ima_hash could still be NULL.
Fixes: 6beea7afcc72 ("ima: add the ability to query the cached hash of a given file")
Signed-off-by: KP Singh <kpsingh@google.com>
Reviewed-by: Florent Revest <revest@chromium.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
1 file changed
